Bottles of this type have to satisfy various constraints associated with their transport and the pouring convenience for the user while having to be as light as possible in order to reduce costs associated with the quantity of plastic material used and to reduce the impact on the environment.
Gripping bottles for pouring their contents poses problems for some users when the capacity reaches 1.5 l, and for the majority of them as of a capacity of 2 l, on account of the transverse dimensions of the body of the bottle, given that the height of the bottle cannot be increased excessively for fear of causing awkward tipping as a result of displacement of the liquid during pouring.
The diameter of the bottles has therefore been reduced in the gripping zone by forming a deep annular groove at the gripping zone as described, for example, in document U.S. Pat. No. 5,385,250. However, such a solution poses problems of resistance to the vertical load to which the bottle is subjected during transport.
Ergonomic hollows have also been formed in the wall of the gripping zone, and document EP-A-0 837 006 may be cited by way of example. Nevertheless, in order to obtain a handle shape which is sufficiently small for the hand of the majority of users, the hollows have to be deep, which results in a large amount of plastic material being used and may pose problems of resistance to large increases in internal pressure which arise during transport.
Moreover, a certain rigidity of the gripping portion is necessary for gripping comfort and in order to avoid liquid being projected as may happen when the user grips an open almost full bottle firmly.
During transport, under the effect of the load of stacked bottles and other factors, the bottles inevitably undergo increases in internal pressure. If a portion of the wall of the body is deformed excessively, the volume of the bottle increases, the internal pressure decreases and the bottle is crushed vertically, which may result in a stack of pallets of bottles tipping. The structural strength could of course be increased by increasing the thickness of the wall, but this runs counter to the requirement of economy of plastic material.
The vertical load supported by the bottle is transmitted from the closing element to the bottom by means of the neck and the body of the bottle where the plastic material is of minimum thickness. The resistance to vertical compression must be accompanied by a certain vertical elasticity which allows the internal pressure of the full bottle to be increased and consequently better resistance to compression provided that the wall of the body, including the gripping portion, is not appreciably radially deformed.